Flower phenotype variation, essential oil variation and genetic diversity among Rosa alba L. accessions used for rose oil production in Bulgaria

• Thirty eight R. alba accessions from IREMC's genetic resources collection were subjected to flower biometric analysis.
• Two flower phenogroups (PG: 1 and PG: 2) were identified.
• PCA analysis of GC/MS data for rose oils distilled from all accessions did not show clear separation between accessions from the two phenogroups.
• SSR analysis at 9 loci revealed identical genotype for all accessions and R. alba Maxima and R. alba Semiplena.
• Selection of a subset of R. alba accessions from the PG: 1 phenogroup is proposed for large scale production of R. alba planting material.

Flower biometric analysis of 38 Rosa alba L. accessions from the genetic resources collection of the Institute of Roses, Essential and Medical Cultures (IREMC), Bulgaria, revealed the existence of two distinct flower phenogroups (PG: 1 and PG: 2), which differ significantly in flower weight, number of flower petals and number of anthers. GC/MS analysis of rose oil samples distilled from the analyzed accessions identified a total of 25 compounds of which 18 compounds were detected in all samples. PCA analysis based on GC/MS data of rose oil samples did not show clear clustering of the rose oils obtained from the two flower phenogroups. Although t-test analysis showed statistically significant variation of the abundances of 6 compounds at P < 0.05 and 4 compounds at P < 0.01 between the two identified phenogroups, the ranges of variation of these compounds among the PG: 1 plants largely overlapped those of the PG: 2 plants. Microsatellite analysis at 9 SSR loci of the studied 38 accessions as well as R. alba Maxima and R. alba Semiplena accessions revealed their clonal origin from a common ancestor. The selection of a small subset of PG: 1 accessions representing the overall diversity of the composition of rose oils distilled from the studied accessions is proposed for industrial production of quality planting material. The necessity to enlarge the R. alba genetic resources pool used for industrial cultivation and rose oil production is further discussed.